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Journal logoSTRUCTURAL SCIENCE
CRYSTAL ENGINEERING
MATERIALS
ISSN: 2052-5206

April 2001 issue

Highlighted illustration

Cover illustration: The structure of Pu31Pt20 [D. T. Cromer & A. C. Larson (1977). Acta Cryst. B33, 2620-2627] viewed nearly perpendicular to a Pu, Pt disc (10 Å thick and 50 Å in diameter) down [111]. Details of the structure were taken from the intermetallics crystal structure database CRYSTMET® using the Materials ToolKit graphics software from Toth Information Systems, Inc.

research papers


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The structure of potassium dinitramide (KDN) has been refined from X-ray diffraction data in the temperature range 85–298 K. The thermal expansion is significantly anisotropic and correlated to the atomic displacement parameters. A rigid-body analysis of the dinitramide anion was carried out. The variation of thermal motion with temperature indicates anharmonicity in the mean field potential.

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An isotropic distortion parameter has been defined that quantifies the departure of the anion skeleton of a crystal from ideal closest-packing. Analysis of the variation in this parameter for a variety of rock-forming minerals at various temperatures and pressures elucidates the important role of anion–anion interactions during expansion and compression.

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Structural, multipole and orbital analyses of the electron density in the rutile-type compounds CoF2 and ZnF2 have been performed using synchrotron X-ray data.

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Structure factors for the Er3Al5O12 and Yb3Al5O12 garnets were measured with synchrotron X-radiation at room temperature. Approximate difference electron density symmetry around the rare-earth atoms was found to reflect that of the cation geometry, emphasizing the importance of second nearest-neighbor interactions.

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The structure of Tl2MoO4 at 293 K has been refined and compared to the structure at 350 K. Second-harmonic generation measurements and symmetry mode analysis have been performed.

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The antifluorite Na2S, disodium sulfide, undergoes, under pressure, two phase transitions adopting the anticotunnite and the Ni2In-type structures. The latter is just the structure which presents the cation array in the high-temperature phases of Na2SO4. An equivalence between oxidation and pressure is established, in the sense that both stabilize the Ni2In-type structure as if the Na and S atoms were recognized in spite of being embedded in an oxygen matrix.

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KTa_{1\ +\ z}O3, an oxide bronze, has been synthesized by electrolytic crystallization. The high-resolution anharmonic crystal structure refinement reveals the presence of Ta2 dumb-bells in the KTaO3 matrix, which explain the semiconductor property.

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The structures of a number of cubic silicate garnets at ambient pressure and under compression have been investigated using first-principles pseudopotential calculations.

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The structure of two intercalated compounds VOPO4–thf and VOPO4–DEG were determined by a combination of high-resolution synchrotron powder diffraction and molecular modelling. Both intercalates exhibit the same type of orientational disorder as observed in VOPO4 intercalated with water.

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The crystal structure of the monoclinic form of 2,2-dihydroxymethylbutanoic acid (C6H12O4) has been determined ab initio using synchrotron radiation powder diffraction data. A partial direct method soluition was completed using Monte Carlo techniques.

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Soft C—H⋯O hydrogen bonds link molecules of substituted diaryl sulfones into aggregates which can be zero-, one-, two- or three-dimensional.

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3,5-Dinitrobenzoic acid forms salt-type 2:1 adducts with a range of organic diamines. The ions are linked into three-component aggregates by N—H⋯O hydrogen bonds, and these aggregates can be further linked by combinations of N—H⋯O and C—H⋯O hydrogen bonds into continuous arrays which may be one-, two- or three-dimensional.

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